A line inversion-based stepwise data driving for low-power mobile TFT-LCDs

This paper proposes a line inversion-based stepwise data driving scheme for use in low-power mobile TFT-LCDs. The proposed stepwise data driving scheme adopts a stepwise pull-up and pull-down transition operations of source and common lines in an LCD penal, resulting in greatly reduced power consumption as compared to the conventional line inversion-based data driving schemes. Moreover, the proposed scheme shows relatively uniform power consumption for different image patterns, making background image design easy for use in commercial portable display devices. Three test chips for mobile devices having QCIF+, QVGA, and HVGA resolutions were fabricated in a 6-V/0.7-μm quadruple-metal CMOS process. The experimental results showed that overall power reductions of 25%-37% for QCIF+, 31%-47% for QVGA, and 42%-53% for HVGA TFT-LCDs were achieved, depending on image pattern, with a die size overhead of less than 1%. They also indicated that the proposed driving scheme allowed around 55% to 32% reduction on image pattern-dependent power variation as compared to conventional driving schemes.